As unseated and exiled dragon prince Viserys Targaryen on HBO’s hit series “Game of Thrones,” Harry Lloyd has had to spend a lot of time on-screen berating and bullying 20-something actress Emilia Clarke, who plays his little sister, Daenerys.

Emilia had just two small television credits before taking on her monstrous role and Harry, an alumnus of the BBC America series “Robin Hood,” said he took the newcomer under his wing from the start, making it easier to dish out some of Viserys’ cruel treatment of the sister he sells as a virgin bride to a nomadic warlord.

“We just became kind of best mates, genuinely,” Harry told Access Hollywood in London of bonding with Emilia on set.

“I kind of took it upon myself to kind of be her big brother a bit and to kind of look out for her,” he continued of their behind-the-scenes relationship in Malta, where the pair shot much of the Targaryen story line. “Also… you want to have a good relationship with someone who you’ve got to be quite horrible to on camera, so at no point mid-scene, you’re worrying, ‘Oh God! I hope I don’t upset Emilia.’

”[It helps] to be close enough with someone to know that they can take it and you can throw it around,” he continued. “The less friendly your relationship is on camera, the more useful it is to be friends with them off camera.”

As the drama continues on HBO in the coming weeks, things are about to get more complicated for the Targaryen siblings as Viserys encounters some very big challenges as his sister’s power – as a result of her marriage to Khal Drogo – grows among the natives.

“She owes everything to him,” Harry said of how Viserys sees his relationship with Daenerys. “She is his sister, his wife and his daughter all kind of in one. Targaryens always wed brother to sister… So for her to have an identity of her own and to become this great kind of warrior princess and to leave me behind, it’s — to say the least — frustrating that no one really understands the importance of my mission.”

With the next several episodes poised to place some real challenges on Viserys’ shoulders, Harry said his character will find himself struggling with some serious internal conflicts.

“He doesn’t really have the maturity to know how to [handle these things]. He believes in his own inherent right, and that often makes him kind of quite spoiled, so he will lash out and that’s kind of the only way [he] knows how to respond,” Harry added.